SEATTLE (AP) — The CEO of electric car company Tesla says a battery that caught fire in a Tesla vehicle was apparently impaled by a metal object.

Elon Musk wrote in a blog post Friday that fires are more common in conventional gas-powered vehicles. It’s safer to power a car with a battery, Musk wrote.

Musk says a curved metal component was apparently the culprit in causing a Tesla to catch on fire Tuesday. He says the object’s shape led to a powerful hit on the underside of the vehicle, punching a 3-inch hole through an armor plate that protects the car’s bottom.

Tesla says the car properly contained the blaze. The driver was able to exit the highway in the Seattle suburb of Kent before flames engulfed the front of the vehicle.